Conventionally, an image forming apparatus forms an image by the development of an electrostatic latent image on a photosensitive drum.
This type of imaging apparatus is equipped with a fully detachable process unit for easy supply of toner. This process unit includes a photosensitive agent cartridge housed with a peripheral mechanism surrounding a photosensitive drum (image carrier), a toner tank that stores toner, and a development roller that carries and supplies toner to the photosensitive drum, etc. In essence, it is an image developing cartridge including a mechanism for development using toner. The image developing cartridge is fully detachable from the photosensitive agent cartridge.
As shown in FIG. 9, the cartridge casing 200 of the photosensitive cartridge contains a photosensitive material drum 201, a transfer printing roller 202 that transfers printing of a visible image (toner image) developed by the toner from an electrostatic latent image on the photosensitive drum 201 to paper P1, a conductive brush 203, and a lower film 204 which is placed so that it blocks a gap between the photosensitive drum 201, and the cartridge casing 200 so that it is able to retain the paper dust removed from the surface of the photosensitive drum 201 by the conductive brush 203 in the cartridge casing 200.
An electrode bias is applied on the conductive brush 203 to remove paper dust from the photosensitive drum 201 to prevent current leakage between the photosensitive drum 201 and the conductive brush 203. The conductive brush 203 is installed in a manner in which it is not in contact with both ends of drum in the axial direction of the photosensitive drum 201.
In other words, the tips of the conductive brush 203 along the axial direction of drum are situated toward the central part of the drum in the axial direction of drum away from the ends of the photosensitive drum 201. To be more precise, the conductive brush 203 is narrower in the lengthwise direction than the photosensitive drum 201 is in the axial direction.
As described above, the lower film 204 is located under the conductive brush 203 and is installed so as to retain the paper dust removed by the conductive brush 203 from the drum 201. In other words, the edge of the lower film 204 in the axial direction of the drum 201 is installed so that the edge extends below the axial direction of drum in relation to the edges of the conductive brush 203 in the axial direction of the drum. That is, the length of the lower film 204 in the axial direction of the drum is slightly longer than the length of the conductive brush 203 in the axial direction of the drum 201.
As described above, in both ends of the drum 201 there are segments that are not in contact with the conductive brush 203 (hereinafter referred to as a non-cleanable area). Hence, the paper dust on the non-contact segments (hereinafter “non-cleanable area”) cannot be removed from the drum 201 by the conductive brush 203.
In other words, the paper dust adhering to the non-cleanable area is the part where the periphery of the photosensitive drum 201 is in contact with the periphery of a development roller (not shown). As a result, the dust may be transferred from the periphery of the photosensitive drum 201 to the periphery of the development roller. The paper dust transferred to the periphery of the development roller will eventually accumulate in 1) the gap between the development roller and a side seal configured to prevent toner leakage from the end of the development roller or 2) in a toner tank which supplies toner to the development roller.
When the paper dust accumulates in the gap between the side seal and the development roller, the paper dust attracts the toner which can cause a toner leak. Additionally, when the paper dust accumulates in the toner tank, the electrostatic charge capacity of the toner in the toner tank is decreased, which can result in uneven toner application to the drum 201.